I agree with giving Garen more changes, but for different reasons. Garen is moderately strong right now, as shown by decent play and win rates (3.86% and 49.28%, respectively, so he could use a buff but not really anything too drastic), and his counterplay's pretty variable: if you have range, high-uptime CC and/or good mobility, he becomes very easy to kite, but against many melee champions, particularly low-mobility ones, he doesn't really present his opponents with the most interesting counterplay. These, and a relatively low overall competitive scalability, are core issues that existed before his Juggernaut update, and have remained mostly unchanged. He technically has a niche now, but his Villain mechanic is entirely contingent on him being able to reach his targets, whereas every other Juggernaut has a means of applying at least some power without being already in melee range of their opponents (Darius has his pull, Illaoi has her E, Skarner has his E and spires, Nasus has his slow, even Mordekaiser has his ult, W and E).
Overall, out of the four juggernauts that got updated, only Darius truly succeeded, and the others either missed the mark somewhat (e.g. Garen and Skarner) or went in the wrong direction (e.g. Morde originally being turned into a duo laner). Unlike the class updates that followed, the M.O. for them was basically to tack on a new mechanic to each of their kits, readjust their stats and see where things went from there, instead of looking into potentially deeper design issues (including their binary relationship with kiting and range, which hasn't quite been resolved properly). This worked for Darius, who basically just needed better sticking power and a way of building tanky DPS to sustain his time-bomb niche, but for the others, they still don't really have the strongest niche or most interesting gameplay, and in Garen's case his Villain mechanic is too unreliable in competitive play to really count as a niche-setter. He needs a way of exerting power that doesn't require him to be directly touching his opponents, and overall his power needs to be made more interesting (his W is still utterly boring, and his Villain buff doesn't have nearly as much strategic gameplay as it would suggest, as priority targets are often unreachable to him, whereas his basic Q-auto-E sequence doesn't give targets many options to react properly to him).